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Multi-Span Sheep House

Single-Span Polyhouses 

Polyhouses are designed to allow much welcomed light and warmth into them. This not only improves food conversion rates but creates a healthier, drier environment which is less susceptable to bacteria and fungi. The notion that a polyhouse is a poor man's livestock house is certainly no longer the case. Advances in structural design, developments in covering materials and improved engineering techniques make polyhouses a modern and inexpensive alternative to traditional livestock housing. 

Our Single-Span polyhouses are suitable for small, medium and large size flocks, or for upland/hill farms where flat ground close by the farm is in limited supply. Single-span structures generally offer higher levels of ventilation, due to the ratio of vented sides to floor space.

Generally speaking, the wider the polyhouse the lower the price per square meter of floor space, making the 9.15m (30ft) wide structure the most economical. If a central feed/access passage is being incorporated into the layout design then the percentage of ‘lost’ housing space is vastly reduced with wider structures. For example, a 9.15m (30ft) wide polytunnel with a 3m (10ft) central passage only loses a third of its livestock area, whereas a 6.4m (21ft) polytunnel with a 3m (10ft) passage would lose almost half.

Extra-High Polyhouses

We supply extra-high polyhouses, ideal for where extra height is required for access by large machinery. These can be either 0.5m or 1m higher than the standard polyhouses. Only recommended with 5ft (1.52m) hoops spacing’s, and are not recommended for exposed locations where severely high wind speeds are expected.  Please phone our sales team for advice and a quotation.

Where these are used for housing calves/cattle we recommend solid clad sides up to 1.0-1.5m above ground level with a 0.5-1m heavy-duty windbreak mesh above this for overhead ventilation.  Our steel side gutters are recommended on calf/cattle houses.

Hoops (Steel Arches)

Our livestock houses are the strongest of their kind. We only supply two-piece hoops – much stronger than 3 or 4 piece hoops used by other manufacturers. For our single span polyhouses we space the hoops either 5ft or 6ft apart. Wider hoop spacings (up to 7ft or 8ft apart) can be catered for, but we would only recommend this for our smaller polyhouses which are being built in relatively sheltered locations.

Generally, 5ft hoop spacings are the most widely used for our 24ft, 27ft and 30ft wide polyhouses, especially where higher wind speeds and heavier snow loads are expected. 6ft spacings are often used for 18ft and 21ft wide polyhouses, or where the weather is less severe. Remember, more steel equals a stronger structure! We use 50mm diameter pre-galvanised steel tube for our 18ft and 21ft wide polyhouses, and 60mm tube for everything above. All hoops have a 1.5mm wall thickness, and our steel tube is galvanised both inside and out.

Straight Sides

All our polyhouses have straight sides to allow for a full working width. The height of the straight sides increases in relation to the tunnel width. Extra high structures are also available.

Foundations

They say any structure is only as strong as it’s foundations. This is why we only use heavy duty galvanised foundations tubes (ground tubes) with a 3.5mm wall thickness give increased protection from corrosion and provide a sound footing. Our unique design allows the polytunnel hoops to be raised up on the foundation tubes (after the polythene cover has been fitted) to achieve a drum-skin finish, this increases your polythene covers life expectancy and protects against wind damage.

Three foundation options are available:

  • Traditional foundation tubes - suitable for both single-span and multi-span polytunnels. A hole measuring approx. 50cm x 50cm x 50cm deep (0.125m³) is required for each foundation tube. This is filled with a standard foundation concrete mix (C20/ GEM3), leaving half of the foundation tube protruding above ground level.
  • Screw anchors - can be manually screwed into the ground with a crowbar using the special adapter (supplied), or mechanically using a mini digger with a hydraulic bit. Only available with single-span polyhouses. Not suitable on ground which has been mechanically disturbed or with a high rubble/stone content. Suitable for use on undisturbed bare ground. Ideal for tenants who may need to relocate in the future, or where a ‘non-concrete’ solution is preferred.
  • Base plates - for bolting on to an existing concrete base. Suitable for single-span and multi-span polyhouses.

Polythene Cover

Polyhouses are designed to allow much-welcomed light and warmth into them. This not only improves food conversion rates but creates a healthier, drier environment which is less susceptible to bacteria and fungi. Our standard polythene cover for agricultural use is white, allowing approx. 65-70% light transmission (30-35% shade value). This is considered to be the correct balance for housing livestock by allowing enough light in to keep the environment dry, whilst preventing excessive heat build-up on warmer, sunny days. 

Alternatively, we can supply a cover which is green on the outside and white on the underside, this allow the structure to be less conspicuous and blend into its surroundings. However, a solid green cover does not allow natural light to pass through, this means additional lighting is required. The white underside optimises artificial light inputs.

Our polythene covers have an average life expectancy of 10 years, this is dependant on the level of care (ie; correct fastening and tensioning, cleaning etc.). All of our polyhouse covers come with a 5-year manufacturer’s guarantee against UV degradation and manufacturing defects.  

PVC Covers

We also offer heavy-duty, PVC-coated fabric covers. Using 610g/m³, flame retardant PVC fabric we can produce covers of any width and length. PVC fabrics offer extra mechanical strength and a life expectancy of up to 20 years. Available in white, green, grey and translucent.

Bracing Bars

Polyhouse brace bars are an optional extra and are only required for polyhouses sited in locations that experience extreme weather conditions, including heavy snow loads and extremely high winds. Brace bars are not required in milder locations, as our polyhouses have been optimised for strength for use in most of the UK. Brace bars are not recommended where additional strength is not necessary, as they limit the access height of machinery to approx. 2.2m high (depending on the width of the polyhouse). Our brace bars are manufactured from heavy-duty 50mm galvanised steel tube. Attached to each side of the hoops (above head height) and supported in the centre with inverted ‘V’ hangers, which creates a type of truss. Increases the wind and snow loading capacity by approx. 20%.

End Frames

We offer two choices for our polyhouse end frames – timber or steel. Timber end frames are produced from 75mm x 75mm (3” x 3”) pressure treated timber, whereas our galvanised steel end frames are manufactured from 75mm x 50mm box section and include gate hanging pins and a gate latch. Door posts can be set at your required width and height but with a max. height of 3.35m for a 3m wide doorway on the standard 9.15m (30ft) wide sheep houses. Extra high sheep houses and calf/cattle houses can have higher doorways. Doors and gates are not normally supplied, however door blinds can be supplied.

The timber we use has been Forest Stewardship Council (FSC) and Programme for the Endorsement of Forest Certification (PEFC) certified, demonstrating our commitment to sustainable forest management.

Side Rails and Ventilation

100mm x 50mm (4” x 2”) treated timber side rails are fitted to both sides, approx. 1m (3ft 3in) off the ground. The sides are then clad with a heavy duty, extruded windbreak mesh (tensile strength of 30kN/m) giving a 63% wind protection factor.

Heavy Duty Mesh Door Blinds (Optional)

Agricultural Mesh Door Blinds are an economic alternative to roller screens. Available as full-height door blinds or ‘above gate’ door blinds. Door blinds are ideal for livestock as they allow good ventilation whilst protecting against severe weather conditions. Easily assembled and simple to operate with pull-cord operation and manufactured from green, heavy-duty, monofilament netting. The width can be reduced during installation where narrower doorways are required.

Strong and durable | UV stabilised | Green Knitted monofilament (no fraying)

Side Gutters (Optional)

Water runoff can be a problem for all farmers. Damp, warm living spaces are a breeding ground for bacteria and fungi. This can be particularly concerning for farmers housing lambs and calves. All our livestock polyhouses are available with optional side gutters, allowing water to be funnelled from the polyhouse roof and can be drained into a livestock drinker. Manufactured from pre-galvanised steel sheet, and include a stop end, down spout, and support brackets. Gutters are usually fitted to both sides of the polyhouse, but can be installed on the windward side only to reduce the cost.

Prices from approx. £3.00 per foot (£10/mtr) per side.

Anti-Hotspot Tape

Padded foam tape which is applied to the upper surface of each hoop prior to the polythene sheet being fitted. It acts as an insulator between the steel tube and the cover, preventing any heat build-up in the steel being transferred to the polythene. It also reduces friction between the hoops and the polythene. Anti-hotspot tape extends the life of the cover by 1-2 years.

Heavy-Duty Fittings

All our brackets and fittings are purpose made in-house and galvanised with electro-plated zinc. It is important that all fittings & brackets can take the strains and loads imposed by wind and snow, hence, we do NOT use cheap, imported, exhaust brackets & keyhole clamps.

Polytunnel Roof Fans (Optional)

Fully automatic roof fans which can be operated on either a temperature or time basis. Very secure and simple to install, requiring no specialist tools. The pressure, which is created when the fan is in operation, lifts the cowl (lid) thus exhausting any unwanted humidity, viruses, heat, stale air etc. When the fan stops the cowl (lid) simply drops under its own weight to close the opening, preventing the ingress of water.

The number of fans required depends on several factors, such as the type of animals housed, the number of animals, age/size, and the amount of natural ventilation which is already present. As a rough guide, we recommend one fan approx. every 10m to 15m (33ft-48ft) along the centre of the roof. They are mainly installed in calf houses. Please call 01282 873120 for further advice and prices.

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Tel: 01282 873120 • Fax: 01282 871733 • Email: info@npstructures.co.uk
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Mill Green, Waterside Road, Colne, Lancs, BB8 0TA